This application claims the benefit of Korean Application No. P96-57881, filed on Nov. 27, 1996, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display and a method of manufacturing the same, and more particularly, to a liquid crystal display which has reduced defects in patterning a pixel electrode connected to a thin film transistor (TFT) and a method of manufacturing the same.
2. Discussion of the Related Art
With reference to FIG. 1, a conventional liquid crystal display is described. A gate bus line 17 is formed in the horizontal direction on a substrate, and a gate electrode 17a is branched off from the gate bus line 17. A data bus line 15 is formed in the vertical direction on the substrate, and a source electrode 15a is branched off from the data bus line. A TFT is formed at the cross-section between the source electrode 15a and the gate electrode 17a, and a drain electrode of the TFT is formed to be connected to a pixel electrode 4.
More detailed structure of the conventional liquid crystal display is described in FIGS. 2 and 3 taken along lines IIxe2x80x94II and IIIxe2x80x94III in FIG. 1, respectively, which show the cross-sectional structures of the TFT and the data bus line. Referring to FIG. 1, the gate electrode 17a branched off from the gate bus line 17 is formed on a transparent substrate 11. The gate electrode 17a is anodic oxidized, forming an anodic oxide layer 35 to improve the insulation property and to prevent hillocks. A gate insulating layer 23 made of an inorganic insulating material, such as SiNx or SiOx, is formed over the surface of the substrate including the gate electrode 17a. A semiconductor layer 22 made of an amorphous silicon is formed on the gate insulating layer 23 to cover the gate electrode 17a. An ohmic contact layer 25 is formed on the semiconductor layer 22. A source electrode 15a branched off from the data bus line and a drain electrode 15b are formed on the ohmic contact layer 25, and are separated from each other at a predetermined distance. A protection layer 26 made of an organic insulating material, such as benzocyclobutene (BCB), is formed to cover the source electrode 15a and the drain electrode 15b. A portion of the organic protection layer 26 is removed to form a drain contact hole. A pixel electrode 4 is formed of a transparent conductive material, such as indium tin oxide (ITO), on the organic protection layer 26 to be connected with the drain electrode 15b through the drain contact hole. The portions A and B in FIGS. 1 and 2 represent the over-etched portions of the pixel electrode 4.
Referring to FIG. 3, a data bus line 15 is formed on the gate insulating layer 23 made of an inorganic insulating material, such as SiNx or SiOx. The protection layer 26 made of organic insulating material, such as BCB, is formed on the substrate including the data bus line 15. The pixel electrode 4 is formed on the protection layer 26. As in FIG. 2, the portions of A and B represent the over-etched portions of the pixel electrode 4, and {circle around (1)} and {circle around (2)} represent portions where light leakage occurs due to the over-etching of the pixel electrode 4.
When indium tin oxide deposited on the organic protection layer is patterned to form the pixel electrode, detachment of the indium tin oxide layer from the organic protection layer may occur, since adhesion between the organic protection layer and the indium tin oxide layer is insufficient. Moreover, a difference in thermal expansion coefficient between the organic insulating material of BCB (50xe2x88x9260xc3x9710xe2x88x926/xc2x0 C.) and indium tin oxide (5xe2x88x927xc3x9710xe2x88x926/xc2x0 C.) and the resultant thermal stress cause micro-cracks in indium tin oxide during the photolithography step for patterning the indium tin oxide layer. Thus, during the subsequent wet etching process of indium tin oxide, an etchant penetrates into the micro-cracks, causing excessive etching of indium tin oxide, known as xe2x80x9ccritical dimension loss (CD loss)xe2x80x9d. CD loss deteriorates contrast and quality of the liquid crystal display.
Accordingly, the present invention is directed to a liquid crystal display and method of manufacturing the same that substantially obviate the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid crystal display and a method of manufacturing a liquid crystal display for preventing over-etching of the pixel electrode during the manufacture, thereby reducing defects in the liquid crystal display and providing an improved manufacturing process of the liquid crystal display.
Another object of the present invention is to provide a liquid crystal display eliminating micro-cracks in the pixel electrode, thereby preventing the CD loss of the pixel electrode.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a method of manufacturing a liquid crystal display, including the steps of sequentially depositing a first layer and a second layer on a protection layer, wherein the first layer has a thermal expansion coefficient less than that of the protection layer and wherein, the second layer has an etch rate greater than the first layer and a thermal expansion coefficient similar to or less than that of the first layer; patterning the second layer on the first layer in a desired pattern; patterning the first layer using the patterned second layer as a mask; and removing the second layer remaining on the patterned first layer.
In another aspect, the present invention provides a method of manufacturing on a substrate a liquid crystal display having a gate bus line, a data bus line, and a switching element with a drain electrode, the method including the steps of forming a protection layer over the substrate to cover the gate bus line, the data bus line, and the switching element; depositing a first layer on the protection layer, the first layer having a thermal expansion coefficient smaller than that of the protection layer; depositing a second layer on the first layer, the second layer having a thermal expansion coefficient substantially consistent with that of the first layer; removing portions of the second layer on the first layer to form a desired pattern of the second layer; removing portions of the first layer using the patterned second layer as a mask to form a desired pattern of the first layer; and removing the second layer remaining on the patterned first layer.
In a further aspect, the present invention provides a liquid crystal display, including a substrate; a gate bus line over the substrate; a data bus line over the substrate; a switching element having a drain electrode over the substrate; a protection layer covering the gate bus line, the data bus line, and the switching element over the substrate, the protection layer having a contact hole over the drain electrode; a first layer on the protection layer, the first layer being connected to the drain electrode through the contact hole and having a thermal expansion coefficient smaller than that of the protection layer; and a second layer on the first layer, the second layer having a thermal expansion coefficient substantially consistent with that of the first layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.